Head up display

Abstract

To provide a head up display capable of displaying an image formed by a plurality of display lights with excellent visibility.SOLUTION: A portable head up display 1 includes: display parts 22, 23 and 24 for generating images formed by two different polarized lights and viewed by a viewer to emit polarized lights related to the images; a control part 25 for controlling the display parts 22, 23 and 24 to generate the images; a reflection member 10 for reflecting the polarized lights toward a viewer; and a reflection rate control structure 15 having the different reflection rates of the two polarized lights in the reflection member 10. The control part 25 generates a correction image obtained by correcting the color of at least one image in the two polarized lights in order to correct a color difference between the images accompanying the reflection in the reflection rate control structure 15.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to head-up displays. [Background technology]

[0002] A head-up display (HUD) is a type of display that reflects a display light from a reflective member such as a windshield of a vehicle, allowing an image to be viewed inside or outside the vehicle. A technology is also known that displays an image in multiple locations by varying the focal lengths of multiple display lights. [Prior art documents] [Patent documents]

[0003] [Patent Document 2] Japanese Patent Application Publication No. 2017-056844 Summary of the Invention [Problem to be solved by the invention]

[0004] With the current widespread use of autonomous driving technology, head-up displays are required to display not only information necessary for driving but also information with entertainment value. At the same time, high image visibility is also required. When attempting to form images based on multiple display lights by reflecting them off a common reflective member, a configuration is required to improve the visibility of each display light.

[0005] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a head-up display that can display an image formed by a plurality of display lights with good visibility. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the head-up display of the present disclosure comprises a display unit that generates images formed with two different polarized lights that are visible to the viewer and emits polarized light related to the images, a control unit that controls the display unit to generate the images, a reflective member that reflects the polarized light toward the viewer, and a reflectance control structure that differentiates the reflectance of the two polarized lights on the reflective member, and the control unit generates a corrected image in which the color of at least one of the two polarized lights is corrected to correct the difference in color between the images caused by reflection by the reflectance control structure. [Effects of the Invention]

[0007] In the head-up display of the present disclosure, an image formed by a plurality of display lights can be displayed with good visibility. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing an example of the system configuration of an embodiment of a HUD according to the present disclosure, illustrating the display of a virtual image V. [Figure 2] FIG. 1 is a diagram showing an example of the system configuration of an embodiment of a HUD of the present disclosure, and is an explanatory diagram showing the display of a real image R. [Figure 3] As an example of an image before color correction, the color shift of the white component is shown on the xy chromaticity diagram of the CIE1931 color space. [Figure 4] As an example of an image after color correction, the color shift of the white component is shown on the xy chromaticity diagram of the CIE1931 color space. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of a head-up display (hereinafter referred to as a "HUD") according to the present disclosure will be described with reference to the accompanying drawings. The HUD according to the present disclosure can be applied to HUDs mounted on vehicles such as automobiles, agricultural machinery, and construction machinery.

[0010] FIG. 1 is a diagram showing an example of the system configuration of an embodiment of a HUD according to the present disclosure, and is an explanatory diagram showing the display of a virtual image V.

[0011] FIG. 2 is a diagram showing an example of the system configuration of an embodiment of the HUD of the present disclosure, and is an explanatory diagram when a real image R is displayed.

[0012] In the following description, "front," "rear," "top," and "bottom" follow the definitions of "Fr.", "Re.", "To.", and "Bo." in Figures 1 and 2.

[0013] The HUD 1 is mounted, for example, in an instrument panel in front of the front seats of a vehicle. The HUD 1 projects and reflects display lights L1 and L2 from the rear and below onto a windshield 10 (a reflective member) of the vehicle. The HUD 1 displays an aerial image consisting of a virtual image V associated with the display light L1 (first polarization, S-polarization) on the outer surface 10b (front) of the windshield 10, i.e., outside the vehicle and in front of the vehicle, for a viewer 3 (e.g., the driver) who is a passenger in the vehicle to view. The HUD 1 also displays an aerial image consisting of a real image R associated with the display light L2 (second polarization, P-polarization) on the inner surface 10a (rear) of the windshield 10, i.e., inside the vehicle, for a viewer 3 to view.

[0014] The display light L1 relates to images that are displayed, for example, during manual driving of the vehicle, to provide information necessary for driving, such as driving speed, engine RPM, blind spot indicator, warning information such as speed limit exceeding warning, route guidance information, etc. The display light L2 relates to characters (assistants, agents) that provide various information to support the driver as the viewer 3, and images (contents) that provide entertainment to the viewer 3, that are displayed, for example, during automatic driving of the vehicle or when the vehicle is stopped.

[0015] The HUD 1 includes a windshield 10 and a display device 20 .

[0016] The windshield 10 has an inner surface 10a and an outer surface 10b, and reflects the display lights L1 and L2 (polarized light) toward the viewer 3. The windshield 10 has a reflective polarizer layer 15 as a reflectance control structure on part of the inner surface 10a. The reflective polarizer layer 15 is disposed on the inner surface 10a in an area onto which P-polarized light, which is the display light L2, is projected. The reflective polarizer layer 15 differentiates the reflectance of the windshield 10 for S-polarized light and P-polarized light (two polarized light). Specifically, the reflective polarizer layer 15 has a higher reflectance for P-polarized light, which is the display light L2, than the reflectance of the windshield 10. The reflective polarizer layer 15 is designed to reflect a large amount of P-polarized light and transmit most of the S-polarized light by setting the reflectance for P-polarized light to 20% or more and the reflectance for S-polarized light to 10% or less, for example, when the incident angle of the display light L2, determined by the relative positions of the display device 20 and the windshield 10, is 55 to 60 degrees. The reflective polarizer layer 15 is formed on the inner surface 10a by, for example, coating or attaching a multilayer thin film.

[0017] The display device 20 includes an image generating unit 21, a first mirror 31, a second mirror 32, a third mirror 33, and a housing 35.

[0018] The image generating unit 21 includes a light source 22 , a display element 23 , a switching element 24 , and a control unit 25 .

[0019] The light source 22 is, for example, a light-emitting diode mounted on a wiring board and emitting white light in the visible wavelength range. The light emitted from the light source 22 is homogenized by passing through optical members (not shown), such as a condenser lens, a lenticular lens, or a diffuser. The display element 23 is, for example, a TFT (Thin Film Transistor) liquid crystal display element. The switching element 24 extracts S-polarized light or P-polarized light as a specific polarization from the display light emitted from the display element 23. Specifically, the switching element 24 passes only the specific polarization while switching between the S-polarized component and the P-polarized component of the extracted display light. The switching element 24 switches the polarization component to be passed by electrical control based on whether or not a current is applied. Here, the S-polarized component of the display light emitted from the display element 23 is designated as display light L1, and the P-polarized component is designated as display light L2.

[0020] The control unit 25 controls the lighting of the light source 22. The control unit 25 also controls the display element 23 to generate a required image (or display light related to the required image). Furthermore, the control unit 25 controls the switching element 24 so that the display light emitted by the switching element 24 switches between S-polarized light and P-polarized light.

[0021] Here, the light source 22, the display element 23, and the switching element 24 function as a display unit that generates images formed with two different polarized lights and viewed by the viewer 3, and emits polarized light related to the images.

[0022] The first mirror 31, the second mirror 32, and the third mirror 33 are flat or curved mirrors. The first mirror 31 reflects the display light L1, which is an S-polarized component, and transmits the display light L2, which is a P-polarized component. The second mirror 32 reflects the display light L2 that passes through the first mirror 31. As shown in FIG. 2, since the first mirror 31 is a mirror that transmits the display light L2, the display light L2 reflected by the second mirror 32 naturally passes from the back side to the front side of the first mirror 31. Therefore, the display light L2 reflected by the second mirror 32 passes through the first mirror 31 again and is guided to the third mirror 33. This allows the second mirror 32 to be disposed close to the first mirror 31, thereby preventing the housing 35 from becoming large.

[0023] The display lights L1 and L2 reflected by the first mirror 31 and the second mirror 32 are guided to the third mirror 33. The third mirror 33 reflects the display lights L1 and L2 and emits them onto the windshield 10.

[0024] The housing 35 supports and houses the image generating unit 21, the first mirror 31, the second mirror 32, and the third mirror 33. The housing 35 has an opening at the top, through which the display lights L1 and L2 reflected by the third mirror 33 are emitted to the outside of the housing 35. The opening is covered with a cover 36 to prevent dust and other particles from entering the inside of the housing 35.

[0025] Next, the operation of the HUD 1 in this embodiment when displaying an aerial image will be described.

[0026] When the HUD 1 displays an aerial image consisting of a virtual image V, the image generation unit 21 emits display light L1 associated with the virtual image V, as shown in FIG. 1 . That is, under the control of the control unit 25, the image generation unit 21 causes the display element 23 to generate an image using light emitted from the light source 22 to display the virtual image V, and further causes the switching element 24 to emit display light L1 consisting of the S-polarized component of the display light. The display light L1 is reflected sequentially by the first mirror 31 and the third mirror 33, and is emitted from the opening. The emitted display light L1 is reflected by the windshield 10 toward the viewer 3, and is viewed by the viewer 3.

[0027] Here, when the first mirror 31, the third mirror 33, and the windshield 10 are considered to be a single imaging optical system, by arranging the image generating unit 21 sufficiently close to the first mirror 31, the composite focus F1 of the imaging optical system is positioned in front of the light source 22. By setting the position of the composite focus F1 in this way, the HUD 1 causes the virtual image V to be visible on the outer surface 10b side of the windshield 10, i.e., in front of the vehicle.

[0028] On the other hand, when the HUD 1 displays an aerial image consisting of a real image R, the image generation unit 21 emits display light L2 corresponding to the real image R, as shown in Fig. 2. That is, in the image generation unit 21, under the control of the control unit 25, the display element 23 generates an image using light emitted from the light source 22 to display the real image R, and the switching element 24 further emits display light L2 consisting of the P-polarized component of the display light. The display light L2 passes through the first mirror 31, is reflected successively by the second mirror 32 and the third mirror 33, and is emitted from the opening. The emitted display light L2 is reflected by the windshield 10 toward the viewer 3 and is viewed by the viewer 3.

[0029] Here, when the second mirror 32, the third mirror 33, and the windshield 10 are considered to be a single imaging optical system, by arranging the image generating unit 21 at a position sufficiently far from the second mirror 32, the composite focus F2 of the imaging optical system is positioned after the light source 22. By setting the position of the composite focus F2 in this way, the HUD 1 allows the real image R to be viewed on the inner surface 10a side of the windshield 10, i.e., inside the vehicle.

[0030] In this way, the HUD 1 (display device 20) projects and reflects display light L1 made of S-polarized light onto the windshield 10 from the inner surface 10a of the windshield 10, causing a virtual image V made of S-polarized light to be viewed on the outer surface 10b of the windshield 10. The HUD 1 also projects and reflects display light L2 made of P-polarized light onto the windshield 10 from the inner surface 10a of the windshield 10, causing a real image R to be viewed on the inner surface 10a of the windshield 10. The HUD 1 displays the virtual image V during manual driving and the real image R during automatic driving or when the vehicle is stopped, for example, based on control by a vehicle ECU that comprehensively controls the vehicle.

[0031] Here, due to the nature of light, reflective materials such as the windshield 10 have different reflectances depending on the polarization. When attempting to display a virtual image V and a real image R using different polarized light as in this embodiment, differences in reflectance will result in differences in the visibility of the images. In the case of S-polarized and P-polarized light used in this embodiment, the S-polarized light has a higher reflectance in principle, which reduces the visibility of the real image R formed by the P-polarized light.

[0032] To address this issue, the HUD1 of this embodiment uses S-polarized light as the display light L1 that displays the virtual image V and P-polarized light as the display light L2 that displays the real image R, and then forms a reflective polarizer layer 15 on the inner surface 10a to increase the reflectance of the P-polarized display light L2, thereby controlling the reflectance. This allows the P-polarized display light L2 to be efficiently reflected by the reflective polarizer layer 15, thereby resolving the issue of insufficient brightness that occurs when the P-polarized light that is the display light L2 has a lower reflectance than the S-polarized light.

[0033] However, since the reflecting surfaces of the display light L1 and the display light L2 are different from those of the windshield 10 and the reflective polarizer layer 15, a deviation (difference) occurs in the color of the image due to the nature of the light.

[0034] 3 is an explanatory diagram showing, as an example, color shift of the white component of an image before color correction on the xy chromaticity diagram of the CIE 1931 color space. In the explanation using FIGS. 3 and 4, color correction of an image (pixel) expressing white W will be described, but color correction can also be performed for colors other than white by applying similar processing.

[0035] When the display light L1 generated by the image generating unit 21 to represent white W on an image is reflected by the windshield 10, a considerable color shift occurs with respect to the white W, and the image is displayed with the color of the coordinate A1. That is, a shift in the magnitude of xa1 and ya1 occurs on the x and y axes in the direction of decreasing the values of x and y (in the direction toward blue) with respect to the white W that is desired to be displayed.

[0036] Furthermore, when the display light L2 generated by the image generating unit 21 to represent white W on an image is reflected by the reflective polarizer layer 15 on the windshield, a larger color shift occurs with respect to the white W than with the display light L1, and the white W is displayed with the color of coordinate B1. That is, a shift in the magnitude of xb1 and yb1 occurs on the x and y axes in the directions that increase the values of x and y (directions that approach red and green) relative to the white W that is desired to be displayed.

[0037] Therefore, a difference in size between (xa1+xb1) and (ya1+yb1) occurs on the x and y axes when viewing the virtual image V and the real image R. This difference in color gives the viewer 3 an uncomfortable feeling, which in turn reduces the visibility and marketability of the HUD 1.

[0038] Therefore, in the HUD1 of this embodiment, in order to correct the difference in color between images caused by reflection on the reflective polarizer layer 15, the control unit 25 generates a corrected image in which the color of the images formed by the two polarized lights is corrected, thereby eliminating the color difference.

[0039] FIG. 4 is an explanatory diagram showing, as an example, a color shift of the white component in an image after color correction on an xy chromaticity diagram of the CIE1931 color space.

[0040] When generating an image with a white color W(wx, wy) using display light L1, i.e., an S-polarized image, control unit 25 controls the image to be generated with the color of coordinate A2, which is expressed by (xa2, ya2) = (wx + xa1, wy + ya1), taking into account the above-mentioned size deviation as a correction amount. As a result, the image expressed with the corrected color is visually recognized as white W(wx, wy).

[0041] Furthermore, when generating an image with a white W(wx, wy) color tone using display light L2, i.e., a P-polarized image, control unit 25 controls the image to be generated with a color tone at coordinates B2, which is expressed by (xb2, yb2) = (wx - xb1, wy - yb1), taking into account the above-mentioned size deviation as a correction amount. As a result, the image expressed with the corrected color tone is visually recognized as white W(wx, wy). As a result, there is no deviation in color tone between the images corresponding to display light L1 and L2, resulting in excellent visibility.

[0042] In this embodiment, the shift amount (xa1,) in color of the P-polarized light, which is the display light L2, is larger than the shift amount in color of the S-polarized light, which is the display light L1. Furthermore, the coordinates A1 and B1 before correction for the images related to the display lights L1 and L2 have the positive and negative values of x and y reversed with respect to white W.

[0043] The HUD 1 in this embodiment described above can display an image formed by the plurality of display lights L1 and L2 with good visibility.

[0044] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the claims. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the inventions described in the claims and their equivalents.

[0045] For example, although the example has been described in which the first polarized light is S-polarized and the second polarized light is P-polarized, the first polarized light may be P-polarized and the second polarized light may be S-polarized. Furthermore, the polarized light is not limited to S-polarized or P-polarized light, as long as the polarization angles of the first polarized light and the second polarized light are different. In this case, it is preferable that the difference in polarization angle between the first polarized light and the second polarized light be 22.5 degrees or more.

[0046] Although the reflectance control structure has been described using an example in which the reflectance of P-polarized light is a reflective polarizer layer 15 that has a higher reflectance than the reflectance of windshield 10, the reflectance control structure may also control the reflectance of S-polarized light, and the type of polarized light to be controlled is not limited as long as the reflectance of the two polarized light is made different.

[0047] Although the control unit 25 has been described using an example in which the color of the images relating to the virtual image V and the real image R is corrected, it is not necessary to correct both images as long as the color of at least one image is corrected to bring it closer to the color of the other.

[0048] In addition, the switching element 24 may be a polarizing plate that is arranged on the display element 23 side, which is the incident side of the display light, and is electrically controlled to rotate around the optical axis direction of the display light as the rotation center axis, thereby switching between passing S-polarized and P-polarized components. [Explanation of symbols]

[0049] 1 Head Up Display (HUD) 3. Viewer 10 Windshield (reflective material) 10a Inner surface 10b External surface 15 Reflective polarizer layer (reflectance control structure) 20 Display device 21 Image Generation Unit 22 Light source 23 Display element 24 Switching element 25 Control Unit 31 First Mirror 32 Second Mirror 33 Third Mirror 35 cabinet 36 Cover F1, F2 composite focus L1, L2 display light R real image V Virtual Image

Claims

1. a display unit that generates images formed with two different polarized lights and that are visually recognized by a viewer, and that emits polarized light relating to the images; a control unit that controls the display unit to generate the image; a reflecting member that reflects the polarized light toward the viewer; a reflectance control structure that differentiates the reflectance of the two polarized lights on the reflective member, The control unit generates a corrected image in which the color of at least one of the two polarized lights is corrected to correct the difference in color between the images due to reflection at the reflectivity control structure.

2. The head-up display according to claim 1 , wherein the reflectance control structure increases the reflectance of the polarized light having a lower reflectance in the reflective member.

3. The head-up display according to claim 1 , wherein the control unit generates the corrected image by correcting the color of the image formed using the polarized light whose reflectance has been increased by the reflectance control structure.

4. The head-up display according to claim 1 , wherein the control unit generates the corrected image by correcting the color tint of the image formed by the two polarized lights.

5. The head-up display according to claim 4 , wherein the control unit corrects the image formed by the polarized light whose reflectance has been increased by the reflectance control structure with a value greater than that of the image formed by the other polarized light.

6. the polarized light whose reflectance has been increased by the reflectance control structure is P-polarized light that allows a real image to be viewed, The head-up display according to claim 2 , wherein the other polarized light is S-polarized light that allows a virtual image to be viewed.

Images